I can read most of the image pdfs from archive.org, but some are blank. From what I can tell, the ones with additional info (like author) embedded don't work. Also, like Boris said, the ones from Google don't show any images that might be there.

When I open one of the blank pdfs, I usually get the full title (not file name) and author in the top margin of the eInk side. There's no way to tell in advance which files will be blank that I've found.

You can try Project Gutenberg if you don't mind the ocr look. They do epub instead of pdf. Many Google books are also in epub format, all the epub files I've downloaded from both sites have worked. For my books, there are a lot of ocr errors and reading through them is a pain.